Method of sueliming benzoic acid



April 8 k: U Q a, e lag Mb I I q -*gm wqlb E i R. H. MCKEE METHOD OF SUBLIMING BENZOIC ACID FiledMarch 29. 1922 $023. mun/6 @MMBH? Inventor @etented Apr;

, trunhppltostton filed Harsh st, 39%. harlot Ho. Ethel? To all whom it may concern:

Be it known that 1, Rates H. hiolinr, a citizen of the United. States, residing at New York,in the count ofNew York, her ough of Manhattan, and State of New York,

have invented certain new anduseful Improvements in Methods of Subliming Benzoic Acid, of which the following is a specification.

My invention more particularly relates C to a method of subliming benzoic acid in accordance with which the material is sublimed at a temperature suficiently low to prevent substantially charring and decomposition of the material. My invention is particularly applicable to the purification of benzoic acid in which the raw material.

operated upon is nearly pure.

Qther objects of my invention will appwr in the specification and will be particularly pointed out in the claim.

In the drawing, 1 have illustrated an apmratus suitable for carryin out no invention, in which 10 is a su liming. ttle 5 0r receptacle, in which is received the henzoic acid 11, which is to be sublimed. The receptacle 10 is preferably, though not necessarily, formed of aluminum, as I have found that this material is not attacked by the molten benzoic acid. Suitable heating means, here shown as com rising heating coils 12, are grrovided for eating the receptacle 10.

e receptacle 10 communicates with the subliming chamber 13 through a passage 14 formed by a pipe 15. A portion 16 of the walls-may be formed of wood or other suitable material impervious to the atmosphere, while at least a portion 17 of the walls, and here shown as the back wall and roof of the chamber, are preferably formed of a material such as canvas, which is. ervious to the atmosphere. The air is withdrawn from the rear end of the chamber 13 by a pi 18 which leads to the receptacle 10 a suite 1e fan or blower 19 being provided for creating a circulation .of neutral gas, preferably air, over the benzoic acid in the subliming kettle and through the subliming chamber. v

By creating a circulatory current of neutral gas over the benzoic acid in the mbliming receptacle an'through the subliming chamber, 1 am to; may out the procem at a temperature C. and not; amve 175 250 0., as in the ordinary process of henzoic acid sublimation. The relatively lower temmrature at which my process is carried out substantially eliminates the char-ring and decomposition of the bcnzoic acid which takes lace in the ordinary process which is carrie out at a temperature around 250 Furthermore, the provision of the circulatory current of neutral gas increases the speed of the sublimation and permits the process to becarried out in approximately half the time for a 'ven amount of material that is ordinari y required. The lower tom erature also reduces, to a large extent, t e heat losses which are incident to sublimation at the higher temperatures.

The provision of the canvas walls in the su'bliming chamber serves to relieve the pressure incident...to the expansion of the gases caused by heating the same, and also permits ready cooling of the vapors and pomibly some difiusion in of fresh air by the circulating air. This portance generally about 160 6., instead of about feature is of im Where crude benzoic acid is furnished to the sublimer in a wet state, this replacement serving to rid the vapors of the moisture, whereas if the sublimer chamber was practimlly airtight, such moisture would be condensed in the finished product which would then be wetter than is commercially desirable.

What I claim and desire to secure by Letters Patent of the United States is:

The process or subliming benzoic acid which consists in heating the benzoic' acid in :a receptacle to a temperature below that at which it substantially chars and in the presence of a neutral s, passing the henzoic acid Va cm with e neutral gas to the subliming c amber, and returning the neutral gas to the heating chamber at a term perature at least as low as that at which it eaves the sublimation chamber.

In testimony whereof I have hereunto signed my name in the presence ct two sub- 10o scribing witneaes.

RALPH l H. Menus. 

